Yes, however if mechanics continuously do paltry damage, it will inevitably encourage bad habits. When you constantly get away with standing in aoes, you won't see them as inherent risks. Why do you think Black Mages and melee stand in so much? Many of them know it won't kill them, so why bother moving? These poor habits that have been cultivated are then taken into your Shinryus, Nidhoggs, Weeping City and Dun Scaiths.
And so begins the cries for nerfs because suddenly, everything they did previously, no longer works.
You know why Temple of Quan is a good dungeon? It made you respect the mechanics. Those bees were going to murder your tank if they weren't stunned or killed. Doom made you pay attention. You rarely see those nowadays hence why dungeons are widely perceived as boring.
As for people making mistakes. That has no bearing on whether the content isn't braindead easy or not. Half the time those mistakes occur because people don't care since dungeons just aren't threatening.
I would also fancy a source. In the quick google search I did, all I found were complaints specifically towards forcing more group oriented content on a playerbase accustomed to solo play, far more linear progression paths and large tedious time sinks (hero points). Complaints of difficulty were certainly not hard to find, but this paints an entirely different paint than the one you have where difficulty was the sole contributing factor.
Admittedly, I do not play GW2. So I may have only scratched the surface here. So do correct me if I'm mistaken.
People advocating for more challenging content what some risk of failure. Examples of that would be Shinryu Normal or The Vault. Both have fairly reasonable challenges when initially released; never demanding too much for story based content but equally not allowing you to mindlessly zone out either. Palace of the Dead's higher floors offer a perfect example of a proper difficulty curve without being too overwhelming, Chimera notwithstanding. You have priority mobs, traps and more branching pathways that all serve to break up the monotony of linear dungeon progression. Mobs on floors 110+ actually hurt too. I can't chain pull them near as easily, if at all, and actually have to rotate CDs on just a single pack. Dungeons? If I'm not blindly pulling everything in sight, I may as well not have CDs because they're utterly useless.
In fact, a friend and I got Kugane Castle a while back. She was on Bard; I on White Mage. Our tank decided to troll at Yojimbo and attempted to get himself locked out. When we caught him, he immediately left. Not wanting to wait, said friend tanked Yojimbo on Bard and you know what, it was probably the most fun I've ever had in Kugane. Why? I actually had to pay attention to her HP. So instead of tossing Regen and forgetting the tank existed while I DPS, I had to weave in both heals and DPS; stopping the latter entirely at some points. Imagine if that were standard boss mechanics. Healers might actually have to heal without mostly Regen.
That's what I want. Not Savage level dungeons or some cutting edge super hard trial. Stuff like the aforementioned, EXs more in the vines of Sephirot and Nidhogg compared to Byakko and Lakshmi and dungeons similar to The Vault and Amdapor Keep.